【PAT】1102. Invert a Binary Tree

考查点：静态数组表示二叉树，中序遍历，BFS

思路：这里不要硬性使用指针表示二叉树，根据输入条件显然用数组表示很方便，而且同样可以进行中序遍历和bfs，题目中的翻转只是幌子，只要接收数据时候左右子树逆序接受就行

#define LOCAL
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#define FOR(i, x, y) for(int i = x; i <  y; i++)
#define rFOR(i, x, y) for(int i = x; i > = y; i--)
#define MAXN 10005
#define oo 0x3f3f3f3f
using namespace std;

const int maxn=150;
struct node{
    int lchild;
    int rchild;
}Node[maxn];
bool h[maxn];
int n,num;

void print(int id){
    printf("%d",id);
    num++;
    if(num<n)printf(" ");
    else printf("\n");
}

void in(int root){
    if(Node[root].lchild!=-1) in(Node[root].lchild);
    print(root);
    if(Node[root].rchild!=-1) in(Node[root].rchild);
}
void BFS(int root){
    queue<int> q;
    q.push(root);
    while(!q.empty()){
        int t=q.front();
        q.pop();
        print(t);
        if(Node[t].lchild!=-1) q.push(Node[t].lchild);
        if(Node[t].rchild!=-1) q.push(Node[t].rchild);
    }
}

int main()
{
    #ifdef LOCAL
        freopen("data.in","r",stdin);
        freopen("data.out","w",stdout);
    #endif // LOCAL
    scanf("%d",&n);
    int root;
    char rchild,lchild;
    FOR(i,0,n)
    {

        scanf("%*c%c %c",&rchild,&lchild);
        if(rchild!='-') Node[i].rchild=rchild-'0';
        else Node[i].rchild=-1;
        if(lchild!='-') Node[i].lchild=lchild-'0';
        else Node[i].lchild=-1;
        h[rchild]=1,h[lchild]=1;
    }
    FOR(i,0,n)
    {
        if(h[i+'0']==0){
            root=i;break;
        }
    }
    BFS(root);
    num=0;
    in(root);

    return 0;
}